The Yeast Assimilable Nitrogen (YAN) Calculator determines the yeast nutrient additions required to supply the desired YAN level in a must. The total YAN requirement is calculated based on the nitrogen requirements of the selected yeast strain and on the initial SG of the must. The required masses of the selected nutrients are then calculated based on their nitrogen contents. The additions can be scheduled in stages, with up to three nutrients added in up to four stages.
Input Field Definitions
Number of Nutrients – The number of yeast nutrients to be used over the course of the fermentation. Up to three nutrients can be selected.
Number of Stages – The number of staged nutrient additions to be used. Up to four stages can be used.
Yeast – The yeast strain to be used. If your yeast strain is not listed, select from one of the three generic entries at the top of the list.
Nutrient (1, 2, 3) – The yeast nutrients to be used in the various stages.
Fermaid O Efficiency Factor – The organic nitrogen in Fermaid O is reportedly utilized by the yeast 3 to 4 times more efficiently than nitrogen in other nutrients. This factor allows the user to account for this enhanced efficiency. It is generally set to a value of 3, and is increased to a value of 4 if GoFerm is used during yeast rehydration. Set it to a value of 1 if you want to ignore it.
Must Volume – The volume of the must being treated.
Must SG – The initial SG of the must being treated. Range: 1.0 to 1.55454
Yeast Multiplier – The factor in mgN/g sugar that is multiplied by the sugar content of the must to calculate the total YAN required. This is initially determined from the yeast strain selected above, but it can be overridden by the user. A range is not enforced, but it should be in the range from 0.5 to 1.5.
Total YAN Required – The total YAN requirements over the course of the fermentation. This is calculated based on the yeast strain and the must SG, but it can be overridden by the user.
Initial Must YAN Level – The estimated initial YAN concentration of the must, prior to the addition of any nutrients. This needs to be estimated by the user.
Relative Mass or YAN Contribution at Each Stage – The relative mass or YAN contribution for each nutrient at each stage. These values determine the mass or YAN allocation between the specified nutrients, as well as the allocation of each nutrient between the stages. The proportional contribution for a given nutrient at a given stage will be the value entered in the corresponding field divided by the sum of the values in all of the fields. These fields are required only if either the number of nutrients or the number of stages are greater than one.
Output Field Definitions
YAN Deficiency – The amount of YAN that needs to be supplied by the added nutrients, which is simply the difference between the total YAN required and the initial must YAN level.
Mass to Add – The mass of each nutrient at each stage needed to supply the total YAN requirements.
Addition Rate – The calculated mass per unit volume of each nutrient at each stage. This allows the user to compare the calculated addition rates to those recommended by the manufacturer or to any legal maximums.
All calculations are based on guidelines in the 2015 and 2016 versions of the Scott Labs Fermentation Handbook. These guidelines recommend calculating the YAN requirements as a function of the sugar content of the must as summarized below in the 2015 Handbook:
This is calculated in FermCalc as:
nt = y·10·Bisgiρw
nt = total YAN requirements, mg/L (ppm)
y = yeast multiplier, mgN/g sugar
Bi = initial Brix of the must
sgi = initial sg of the must
ρw = density of water = 0.9982 g/mL at 20°C (68°F)
The table below compares the results of equation (8-10) for values of y of 0.90 and 1.25 to the recommended YAN levels of Bisson and Butzke (2000), which are cited frequently on other web sites. It can be seen that the Bisson and Butzke recommendations generally fall between the Scott Labs medium and high recommendations. FermCalc gives the user the ability to override the yeast multiplier and/or the calculated YAN requirement.
|°Brix||g/L Sugar||YAN Requirements mg/L|
y = 0.90
y = 1.25
The YAN deficiency is the total YAN requirement minus the initial must YAN level, assuming that the contribution of yeast rehydration nutrients are negligible:
nd = nt – nm
nd = YAN deficiency, mg/L (ppm)
nm = initial must YAN level, mg/L (ppm)
Masses to be added are calculated from the nitrogen balance:
v·nd = Σmijni
v = must volume, L
mij = mass of nutrient i required at stage j, mg
ni = nitrogen content of nutrient i, fraction
Yeast multipliers based on the Scott Labs guidelines are listed below:
|Lallemand||Lalvin||ICV Opale 2.0||Low||0.75|
|Lallemand||Uvaferm||CEG (Epernay II)||Med||0.9|
Nutrient requirements for some other yeast strains not listed above are provided by Pambianchi, both in his book Modern Home Winemaking: A Guide to Making Consistently Great Wines (2021) and online here. The Pambianchi relative nutrient requirements scale (low/mid/high) appears to be consistent with the Scott Labs definitions.
Yeast nutrient nitrogen contents are listed below. This list includes only those nutrients which should be added directly to the fermenter, and does not include yeast rehydration nutrients. Many of the listed nutrients contain DAP and/or thiamine. The Alcohol and Tobacco Tax and Trade Bureau (TTB) sets the maximum legal addition rate for DAP at 8 lbs. per 1000 gals. (0.96 g/L), and for thiamine at 0.005 lb/1000 gals. (0.6 mg/L). FermCalc does not enforce any limits, so it is up to the user to ensure that the nutrient additions comply with the limits set by the TTB and by the manufacturer.
|Manufacturer||Nutrient||% Nitrogen||Data Source|
|Various||Diammonium Phosphate (DAP)||21||Manufacturer|
|Lallemand||Fermaid K||10||Scott Labs|
|Oenobrands||Nutrivin||15||Email from manufacturer|
|Oenobrands||Nutrivin Super||13||Email from manufacturer|
|IOC||Phosphate Titres||21||Scott Labs|
|Country Wines||Super Ferment||6.53||Email from manufacturer|
For more information about nutrient additions, see Travis Blount-Elliott’s white paper.